Entomocidal activity of some botanical powders and their mixes against adults of Lasioderma serricorne Fabricius and Stegobium paniceum Linnaeus (Coleoptera: Anobiidae)

The study investigated the lethality of powders made from rice husk ash (RHA), dry flower buds of Eugenia aromatica (L.) Baill. (EAP), and dry seeds of Piper guineense Schumach. (PGP), to adults of Lasioderma serricorne Fabricius and Stegobium paniceum Linnaeus, at 25 ± 2 °C and 65 ± 3% relative humidity. The powders were tested singly, and in binary and ternary combinations at the dosages of 0.02, 0.04, 0.06, 0.08 and 0.1 g/10 g of grain in glass Petri dishes. The constituents of binary and ternary combination of powders were mixed in equal proportions. There was a control involving no powder. Adult mortality of 20 individuals was observed 3, 5 and 7 days post treatment. ANOVA of data indicated significant differences among treatment means. Adult mortality increased with increase in dosage of powders and period of exposure. When applied singly the three insecticidal powders generally showed decreasing lethality to the adults beetles in this order RHA > EAP > PGP with respect to S. paniceum, but EAP > RHA > PGP with respect to L. serricorne. In the binary and ternary combinations of equal proportions the less toxic powders were more enhanced in lethality. The use of the binary and ternary combinations may be favoured for use in mitigating S. paniceum and L. serricorne damage to stored products for reasons of affordability, sustainability and durability which is discussed.